Here is the synopsis from JCPA (which, by the way, is one of the great things about all JCPA articles - the fact that they put the important points as bullet items):
How do we resolve the dilemma of a peace agreement that includes handing over the Golan Heights to the Syrians, while facing the fact that Israel cannot be defended without the Golan Heights? The way around this was supposed to be the inclusion in any peace agreement of specific security arrangements. Yet this approach was based on a number of assumptions, all of them misguided.Seriously, read the whole thing.
Events over the past ten years have also revealed a marked change in the types of threats to be expected from a Palestinian state or from the existing Palestinian entity. This involves a switch to three types of weaponry that all fundamentally contradict the guidelines discussed for security arrangements.
Rockets and missiles positioned throughout the West Bank would easily cover the entire State of Israel. Advanced anti-aircraft missiles would be capable of shooting down not only large passenger aircraft flying into Ben-Gurion International Airport, but also helicopters and even fighter planes. Anti-tank missiles that are highly effective up to a range of 5 km. can easily cover not only strategic positions such as Israel's north-south Highway 6, but well beyond.
The common denominator among all of these is the ease of smuggling and clandestine manufacture, as is taking place today in Gaza. No monitoring system that may be established will be able to prevent this. Only effective control of the Jordan Valley along the Israeli-Jordanian border can prevent the smuggling of these types of weapons.
In addition, if Israel were to withdraw to the 1949 armistice lines, then the area to the east of the Israel-Palestine border would be home not only to the Palestinian Authority, but to other potential enemies too, including Hizbullah and Syria. This means that in determining security arrangements in the West Bank, the approach must be broader, beyond Israel's needs vis-à-vis only the Palestinians.